BRAKE PAD

Abstract

Brake pad (18), the pad (18) comprising a friction material lining (20) having a friction face (22A) for contacting a rotating element, a leading edge (22E) and a trailing edge (22F), the lining (20) having at least one main collection groove (30, 32), the pad (18) further comprising at least one suction hole for fluidic communication with said at least one main collection groove (30, 32), said at least one suction hole also being for connection to a vacuum source, wherein said at least one main collection groove (30, 32) comprises a first portion open on the friction face and a second portion covered by friction material of the friction face (22A). Figure 7

Description

Title of the invention: BRAKE PAD Technical field

[0001] The present disclosure relates to the field of brake pads. Prior art

[0002] Conventionally, vehicle braking systems comprise a brake pad which, during braking phases, comes to bear against an element rotating around an axis of rotation, thus causing the vehicle to brake. In particular, in railway vehicles, such as trains, trams or metros, braking is carried out by means of a shoe brake, also called a block brake or TBU (by its acronym in English "Trader Brake Unit"). In this type of brake, the brake pad, also called a shoe or block, comes to bear, during braking phases, on a radially external surface of a moving wheel of the railway vehicle.

[0003] The pad of the shoe brake comprises a lining made of friction material. One face of this lining which comes into contact with the wheel during braking phases, called the friction face, as well as the wheel itself, gradually wears by abrasion, which generates particles. Since these particles are polluting, it is appropriate to limit their release into the environment. To this end, the lining is conventionally provided with a particle collection groove which is completely open on the friction face and which extends over almost the entire width of the pad, as described in FR 3087238 AL. This groove is fluidically connected to a source of depression capable of sucking up the collected particles.

[0004] The wear of the friction face allows the pad to match the shape of the vehicle wheel. In particular, from a certain level of wear, the radius of curvature of the pad corresponds to the radius of curvature of the wheel. Thus, once such a level of wear is reached, the opening on the friction face of the collection groove is completely closed by the wheel during braking phases. This limits the loss of collected particles and therefore improves the efficiency of the suction.

[0005] It is well known that the diameter of the wheel varies during its service life due to wear and successive reprofiling. In particular, the diameter of a new wheel can be between 50 mm and 150 mm greater than the diameter of the same worn wheel. In addition, the lateral position of the wheel relative to the pad is specific to each wagon-bogie pair. Consequently, it is difficult to design a pad that perfectly matches the shape of the wheel when it is put into service, which means that, during braking phases, the collection groove is not completely closed before a minimum level of wear of the friction face. Particles generated during braking phases braking by contact between the lining and the wheel can therefore escape and pollute the environment.

[0006] In order to overcome this drawback, it has been proposed to provide the wafer with shorter collection grooves. However, reducing the size of the groove also reduces the efficiency of particle collection in the groove, since a large portion of the particles are not caught in the collection groove.

[0007] There is therefore a need to design a brake pad allowing the collection and suction of most of the particles formed by abrasion during braking phases, while limiting the risk of leakage of the collected particles as long as the pad does not perfectly match the shape of the wheel. Summary

[0008] For this purpose, a brake pad is proposed, the pad comprising a lining of friction material having a friction face intended to come into contact with a rotating element, a front edge and a rear edge, the lining being provided with at least one main collection groove, the pad further comprising at least one suction hole intended to be in fluid communication with said at least one main collection groove, said at least one suction hole also being intended to be connected to a source of vacuum, in which said at least one main collection groove comprises a first part open on the friction face and a second part covered by friction material of the friction face.

[0009] The second part of the at least one main collecting groove being covered by friction material, this second part of the at least one main collecting groove is open on the friction face only after the friction material covering it has been completely worn by the abrasion of the pad in contact with the rotating element during the braking phases. In particular, the second part of the at least one main collecting groove is, initially, immersed in the lining. As the friction face of the pad wears by contact with the rotating element, the second part of the main collecting groove emerges and opens on the friction face.This prevents the second part of the main collection groove from being opened on the friction face before the level of wear of the pad is sufficient for the rotating element to close the second part of the at least one main collection groove during braking phases. This limits the risk of particles resulting from the wear of the pad and the rotating element, and collected in the at least one main collection groove, escaping through the second part of the main collection groove before being sucked in by the vacuum source. In other words, the at least one main collection groove becomes sealed earlier than in the pads of the prior art. The efficiency of collecting and suctioning these particles is thus improved, since fewer particles are lost than if the main collection groove was originally completely open on the friction face.

[0010] In the present text, when it is indicated that any groove becomes “watertight”, it is meant that the groove is closed by the rotating element when the plate comes into contact with it.

[0011] The pad is for example a shoe (or block) of a shoe brake (or block brake, or TBU) of a railway vehicle. Alternatively, the pad may be a pad for a brake of a road vehicle or of a stationary rotor machine such as a wind turbine or an industrial machine.

[0012] The plate may further comprise a lining carrier which is shaped to be connected to a sole carrier, for example via a pin configured to pass through at least one orifice provided in the lining carrier. The lining carrier may be connected to a face of the lining, called the fixing face. The fixing face may be opposite said friction face in a direction substantially perpendicular to the friction face.

[0013] The lining holder may comprise a sheet metal, made for example of metallic material.

[0014] The at least one main collecting groove may extend in depth between the friction face and the attachment face. The main collecting groove is preferably a blind groove at an opposite end, in the direction connecting the friction and attachment faces, to its opening on the friction face.

[0015] The rotating element is for example a wheel of a railway vehicle. The rotating element may alternatively be a brake disc. According to one example, the rotating element rotates about an axis of rotation which is substantially perpendicular to a radial direction of said rotating element.

[0016] A radially outer surface of the wheel may have a substantially frustoconical shape. In particular, a diameter of the wheel may gradually increase between an axially inner face and an axially outer face of the wheel. The rotating element may comprise a flange projecting radially from the axially inner face of the wheel. The frustoconical shape and / or said flange reduce the risk of derailment of the vehicle.

[0017] In the present text, "axial" means in a direction substantially parallel to the axis of rotation of the rotating element, while "radial" means any direction substantially perpendicular to the axis of rotation of the rotating element.

[0018] As the vehicle moves, the wheel gradually wears, so that the diameter of a new wheel is greater than the diameter of the same worn wheel.

[0019] When the pad is included in a braking system for a railway vehicle, it is configured to, during braking phases, come to bear on the rotating element according to the radial direction of this rotating element.

[0020] In this text, the "front edge" of the wafer means the edge of the wafer that is first seen by a specific point imagined on the rotating element when the latter rotates about its axis of rotation. Similarly, the "rear edge" of the wafer means the edge of the wafer that is last seen by the specific point imagined on the rotating element when the latter rotates about its axis of rotation.

[0021] The suction hole is for example a hole passing through the lining between an edge or a face thereof and a portion of the at least one main collection groove. Alternatively, the suction hole is for example a hole passing through the lining between an edge thereof and a portion of a groove fluidly connected to the at least one main collection groove. In some cases, when several main collection grooves are provided, a respective suction hole is provided for each main collection groove. In other cases, a single suction hole may be provided for suctioning particles from several main collection grooves fluidly connected to each other.

[0022] The source of depression is for example a particle vacuum cleaner. Communication means, such as a flexible pneumatic hose, can connect the source of depression to the suction hole.

[0023] According to one aspect, said friction face may comprise a chamfered edge extending between said front edge and said rear edge, the second portion of the at least one main collection groove being disposed at least partly under said chamfered edge.

[0024] The chamfered edge is for example arranged opposite the flange of the rotating element. The contact between this chamfered edge and the rotating element generally takes place later than the contact between the rest of the insert and the rotating element. Also, the wear of the chamfered edge begins later than the wear of the rest of the insert when the friction face comes into contact with the rotating element. The second part of the at least one main collection groove being arranged at least partly under the chamfered edge, it is prevented that particles collected in the at least one main collection groove can escape through the chamfered edge which is not yet in contact with the rotating element when other parts of the insert are already in contact with this rotating element. At the same time, thanks to the presence of said second part, the collection groove extends over a larger surface area.

[0025] According to one example, the entire second portion of the at least one collection groove is arranged under the chamfered edge.

[0026] The chamfered edge may connect the front and back edges. For example, the edge chamfered is substantially perpendicular to each of the front and rear edges. The front and rear edges are, for example, substantially parallel to each other.

[0027] According to one aspect, the liner may comprise a first main collection groove disposed proximate said front edge and a second main collection groove disposed proximate said rear edge.

[0028] In the present text "near the front / rear edge" is understood to mean being arranged at a distance from the front / rear edge less than or equal to 20% of the distance separating the front and rear edges, preferably less than or equal to 10% of the distance separating the front and rear edges.

[0029] The presence of said first and second main collection grooves near the front and rear edges of the lining of the pad makes it possible, regardless of the direction of rotation of the rotating element, to collect particles resulting from the abrasion of the lining and the rotating element in at least one collection groove. The suction of polluting particles is therefore possible regardless of the direction of rotation of the rotating element.

[0030] According to one aspect, the first main collecting groove may extend in length substantially parallel to said front edge and the second main collecting groove may extend in length substantially parallel to said rear edge. The first collecting groove and the second collecting groove may thus be adjacent over their entire length to the front edge and the rear edge respectively. The length of each collecting groove is understood here to be the dimension of this groove which is included in the plane of the friction face of the lining.

[0031] According to one aspect, the first main collection groove may extend in depth non-parallel to said front edge and the second main collection groove may extend in depth non-parallel to said rear edge.

[0032] Indeed, in some cases, the first collecting groove may not be parallel to the front edge of the lining over its entire depth, and / or the second collecting groove may not be parallel to the rear edge of the lining over its entire depth (this depth is understood here as the dimension of the first and second collecting grooves which extends between the friction face to the attachment face of the lining). This can happen even when the first collecting groove is substantially parallel to the front edge and / or the second collecting groove is substantially parallel to the rear edge over their entire length (understood here, as indicated previously, as the dimension of the first groove and the second groove included in the plane of the friction face).In this way, the portions of lining between the front edge and the first collecting groove, and / or between the rear edge and the second collecting groove gradually increase between the friction face and the fixing face, thereby reducing the stresses on the lining and . therefore the risk of breakage of these portions. According to a non-limiting example, the first and second collection grooves may not be parallel to the front and rear edges over their entire depth when the front and / or rear edges are inclined between the friction face and the attachment face of the lining.

[0033] According to one aspect, the pad may further comprise a secondary collection groove disposed between the first main collection groove and the second main collection groove, said at least one secondary collection groove being at least partly open on said friction face.

[0034] The presence of the first and second main collection grooves, and of the secondary collection groove, has the advantage of ensuring that, regardless of the radius of curvature of the friction face of the lining, the support of the friction face of the lining on the wheel during braking phases is opposite one of the collection grooves. It is thus possible to collect in the collection grooves a greater quantity of the polluting particles emitted by the abrasion of the pad and the wheel. In addition, as indicated previously, the presence of the first and second main collection grooves near the front and rear edges respectively makes it possible to ensure the collection of the polluting particles regardless of the direction of rotation of the wheel.

[0035] The secondary collection groove may be located in a central position of the liner. By "central position" is meant here a position located substantially the same distance from the front edge as from the rear edge of the liner. Alternatively, the secondary collection groove could be closer to one of the front or rear edges of the liner, than to the other of these front and rear edges.

[0036] The secondary collection groove may extend substantially parallel to the first and second main collection grooves, but this is not limiting. For example, the secondary collection groove could be substantially parallel to only one of the two main collection grooves. In another example, the secondary collection groove may extend in a direction not parallel to the first and second main collection grooves.

[0037] According to one aspect, said secondary collection groove may comprise a first portion open on said friction face and a second portion covered by friction material of the friction face.

[0038] As for the main collecting grooves, thanks to the second part covered by friction material, this second part of the secondary collecting groove is open on the friction face only after the friction material covering it has been completely worn by the abrasion of the pad in contact with the rotating element during the braking phases. In particular, the second part of the secondary collecting groove is, initially, immersed in the lining. As the friction face of the pad wears through contact with the rotating element, the second part of the secondary collection groove emerges and opens onto the friction face. This prevents the second part of the secondary collection groove from being opened onto the friction face before the level of pad wear is sufficient for the rotating element to seal the second part of the secondary collection groove during braking phases. This limits the risk of particles resulting from the wear of the pad and the rotating element, and collected in the secondary collection groove, escaping through the second part of the secondary collection groove before being sucked in by the vacuum source. In other words, the secondary collection groove becomes sealed more quickly.The efficiency of collecting and suctioning polluting particles is thus improved, since fewer particles are lost than if the secondary collection groove was originally completely open on the friction face.

[0039] The second portion of the secondary collection groove may be disposed entirely beneath the chamfered edge. Alternatively, a portion of the second portion of the secondary collection groove may be submerged beneath the friction material of the friction face of the lining, the remainder of the second portion of the secondary collection groove being submerged beneath the chamfered edge. From a certain level of wear of the lining, the submerged second portion of the secondary collection groove may emerge, i.e., open onto the friction face of the lining.

[0040] In some cases, the secondary collecting groove is fully open on the friction face of the lining even when the pad is new. In such cases, advantageously the secondary collecting groove is shorter, for example it has no portion extending into the chamfered edge.

[0041] Of course, the lining may comprise a plurality of secondary collection grooves as described in the present text.

[0042] According to one aspect, said secondary collection groove is fluidly connected to said first main collection groove and to said second main collection groove.

[0043] According to one example, channels may be provided within the liner fluidly connecting the secondary collection groove to said first main collection groove and said second main collection groove. Alternatively, the secondary collection groove may extend so as to be directly connected to said first main collection groove and said second main collection groove.

[0044] According to one aspect, the wafer further comprises a first transverse collection groove fluidly connecting the first primary collection groove to the secondary collection groove, and a second transverse collection groove. fluidly connecting the second primary collection groove to the secondary collection groove.

[0045] Thanks to the transverse collection grooves, the entire length of the lining between said first main collection groove and said second main collection groove can be crossed by at least one collection groove, which makes it possible to increase the quantity of polluting particles resulting from the abrasion of the lining and the wheel which are collected in the collection grooves. This reduces the quantity of polluting particles released into the environment.

[0046] According to one aspect, the first transverse collection groove is at least partly open on the friction face and extends obliquely between the first main collection groove and the secondary collection groove, and the second transverse collection groove is at least partly open on the friction face and extends obliquely between the second main collection groove and the secondary collection groove.

[0047] In the present text, when it is indicated that the transverse collection grooves extend "at an angle" it is understood that they form a non-zero and non-right angle with each of the grooves that they connect. In this case, the first transverse collection groove forms a non-zero and non-right angle with the first main collection groove and the secondary collection groove, while the second transverse collection groove forms a non-zero and non-right angle with the second main collection groove and the secondary collection groove.

[0048] The fact that the first and second transverse collection grooves extend at an angle allows that during braking phases, the radially external surface of the wheel wears homogeneously, without generating excess thickness on this radially external surface, as will be detailed later.

[0049] The first transverse collection groove may extend between one end of the first main collection groove located opposite the axially outer edge of the lining, and one end of the secondary collection groove located opposite the chamfered edge.

[0050] The second transverse collection groove may extend between one end of the second main collection groove located opposite the axially external edge of the lining, and the end of the secondary collection groove located opposite the chamfered edge.

[0051] The first and second transverse collection grooves may be open over their entire extension on the friction face. It is however possible to provide submerged portions on each of the first and second transverse collection grooves.

[0052] According to one aspect, the plate comprises a single suction hole opening onto one of said secondary collection groove, said first collection groove main and to said second main collection groove.

[0053] Thus, from a single suction hole, it is possible to suck the particles collected in said secondary collection groove, in said first main collection groove and in said second main collection groove. The manufacture of the wafer is thus facilitated. In addition, the size of the assembly formed between the vacuum source, the communication means and the wafer is reduced.

[0054] According to a non-limiting example, the suction hole is arranged at one end of one of the main collection grooves or the secondary collection groove. This concentrates the suction of the particles at this end. According to one example, the suction hole opens onto one end of the secondary collection groove which is opposite the axially external edge of the lining.

[0055] The suction hole is for example arranged in the lining of the plate so as to fluidically connect one of the collection grooves to the external environment.

[0056] According to another example, an individual suction hole may be provided for each of the main collection grooves and for the secondary collection groove. This configuration is notably implemented when the main and secondary collection grooves are not fluidly connected to each other, but of course it could also be implemented when all these collection grooves are fluidly connected to each other. According to a non-limiting example, the individual suction hole is arranged at one end of the respective collection groove, which makes it possible to concentrate the suction of the particles at this end.

[0057] In some cases, the lining may further comprise at least one orifice which passes through the chamfered edge. Each orifice may open into one of the main collection grooves or the secondary collection groove. An air flow may thus enter the collection grooves through the orifice. By the action of the vacuum source, this flow then circulates in the collection grooves until it reaches the suction hole and the pneumatic pipe, which allows the evacuation of the particles collected in the collection grooves of the lining. Thanks to each orifice, the particle suction performance is independent of the level of wear of the lining. Brief description of the drawings

[0058] Other characteristics, details and advantages will appear on reading the detailed description below, and on analyzing the attached drawings, in which: Fig.l

[0059] [Fig.l] shows a schematic perspective view of a braking system according to an example of realization. Fig. 2

[0060] [Fig.2] shows a schematic side view of a brake assembly of the braking system of [Fig. 1]. Fig. 3

[0061] [Fig.3] shows a front schematic view of a detail of the braking system of [Fig.l]. Fig. 4A

[0062] [Fig.4A] shows a schematic side view of a rotating element and a brake pad of the braking system of [Fig.l] according to a first configuration. Fig. 4B

[0063] [Fig.4B] shows a schematic side view of a rotating element and a brake pad of the braking system of [Fig.l] according to a second configuration. Fig. 5A

[0064] [Fig.5A] shows a schematic perspective view of a brake pad of the braking system of [Fig.l] according to a first exemplary embodiment. Fig. 5B

[0065] [Fig.5B] shows a schematic cross-sectional view of the plate of [Fig.5A]. Fig. 6

[0066] [Fig.6] shows a schematic perspective view of a brake pad of the braking system of [Fig.l] according to a second exemplary embodiment. Fig. 7

[0067] [Fig.7] a schematic perspective view of a brake pad of the braking system of [Fig.l] according to a third exemplary embodiment. Fig. 8

[0068] [Fig.8] presents a table schematically showing a contact surface of the friction face of different types of brake pads, including the pads of the examples of Figures 5A to 7, for a first level of wear of these pads depending on whether a rotating element of the braking system of [Fig.l] is new or worn. Fig. 9

[0069] [Fig.9] shows the table of [Fig.8] for a level of pad wear higher than that of [Fig.8]. Fig. 10

[0070] [Fig. 10] shows the table of figures 8 and 9 for a level of wear of the pads higher than that of [Fig.9]. Fig. 11

[0071] [Fig.11] shows the table of figures 8, 9 and 10 for a level of wear of the pads higher than that of [Fig.8]. Fig. 12

[0072] [Fig. 12] shows a graph representing, for the case where the rotating element of the braking system is new, an evolution of the cumulative efficiency of particle suction as a function of the life rate of the pad for the types of pads presented in Figures 8 to 11. Fig. 13

[0073] [Fig. 13] shows a graph representing, for the case where the rotating element of the braking system is worn, an evolution of the cumulative efficiency of particle suction as a function of the life rate of the pad for the types of pads presented in Figures 8 to 11. Description of the embodiments

[0074] [Fig.l] shows an example of a braking system 10 for a vehicle, in particular a railway vehicle (train, tram, metro, etc.). The braking system 10 comprises a rotating element 12 and a brake assembly 14.

[0075] The rotating element 12 corresponds to a part of the vehicle causing translational movements of the vehicle thanks to a rotational movement of this element 12 around an axis of rotation. In this case, the rotating element 12 is a wheel of the vehicle configured to rotate around an axis of rotation A.

[0076] Advantageously, a radially external surface 16 of the wheel 12 has a substantially frustoconical shape. In particular, a diameter of the wheel 12 increases progressively between an axially internal face 13A and an axially external face 13B of the wheel 12. In the present text, the axial direction corresponds to any direction substantially parallel to the axis of rotation A, and the radial direction corresponds to any direction substantially perpendicular to the axis of rotation A. Such a frustoconical shape of the radially external surface 16 makes it possible to guarantee the self-centering of the wheel 12 during the translation of the vehicle, and limits the risk of derailment of the latter in the curves present in its path.

[0077] As visible in [Fig.l], the wheel 12 may also comprise a flange 17 projecting radially from the axially internal face 13A of the wheel 12. Such a flange 17 also reduces the risk of derailment of the vehicle.

[0078] When the vehicle moves, the wheel 12, and in particular its radially external surface 16, gradually wears. Also, a diameter of the new wheel 12 differs from the diameter of the worn wheel 12. Generally, the diameter of the new wheel 12 is greater than the diameter of the worn wheel 12. For example, the diameter of the new wheel 12 may be between 50 mm and 150 mm greater than the diameter of the same worn wheel 12. According to a non-limiting example, the diameter of the new wheel 12 is 860 mm, while the diameter of the worn wheel 12 is 790 mm.

[0079] The brake assembly 14 comprises a brake pad 18, also called a shoe or block. The pad 18 comprises a lining 20 made of friction material. The lining 20 comprises a first face, called the friction face 22A, arranged radially opposite the radially external surface 16 of the wheel. The friction face 22A is substantially curved. When the pad is new, the friction face 22A has a radius of curvature RI (Figs. 4A and 4B).

[0080] As will be detailed, the friction face 22A is intended to come into contact with a portion of the radially external surface 16 of the wheel 12 during the braking phases of the vehicle. Generally, when the pad 18 is new, the radius of curvature RI of the friction face 22A is different from a radius of curvature R2 of the portion of the radially external surface 16 of the wheel 12 on which the friction face 22A comes into contact during the braking phases. Also, when the pad 18 is new, the entire friction face 22A is not in contact with the radially external surface 16. When the radius of curvature RI of the friction face 22A is greater than the radius of curvature R2, as illustrated in [Fig.4A], only a central portion of the friction face 22A is in contact with the radially external surface 16, the ends of the friction face 22A being at a distance from the radially external surface 16.On the contrary, when the radius of curvature RI of the friction face 22A is less than the radius of curvature R2, as illustrated in [Fig.4B], the central part of the friction face 22A is at a distance from the radially external surface 16, the ends of the friction face 22A coming into contact with the radially external surface 16.

[0081] In the following, it is considered that the radius of curvature RI of the friction face 22A is greater than the radius of curvature R2, without this being limiting.

[0082] The lining 20 comprises a second face 22B, called the fixing face, opposite the friction face 22A. In particular, the friction faces 22A and the fixing faces 22B are opposite in the axial direction.

[0083] The lining 20 further comprises an axially internal edge 22C, an axially external edge 22D, a front edge 22E, and a rear edge 22F. The edges 22C, 22D, 22E and 22F extend substantially radially between the friction 22A and fixing 22B faces.

[0084] The axially inner edge 22C and the axially outer edge are opposite in the axial direction. These edges 22C, 22D connect the front edge 22E and the rear edge 22F to each other.

[0085] As can be seen in [Fig.3], the axially internal edge 22C is axially opposite the flange 17 when the plate 18 is in contact with the wheel 12. As can be seen from this figure, the axially internal edge 22C can be chamfered.

[0086] The front edge 22E and the rear edge 22F are defined with respect to a direction of rotation of the wheel 12. In the example of [Fig.l], it is assumed that the wheel 12 rotates in a direction R around the axis A. The front edge 22E corresponds to the edge of the lining 20 which is seen first by a specific point P imagined on the wheel 12 when it rotates around its axis of rotation A in the direction R, while the rear edge 22F corresponds to the edge of the lining 20 which is seen last by the specific point P when the wheel 12 rotates around its axis of rotation A in the direction R. Of course, the direction of rotation R could be opposite to that marked in [Fig.l], which would reverse the position of the front 22E and rear 22F edges.

[0087] As will be detailed later, the lining 20 comprises at least one particle collection groove.

[0088] The brake assembly 14 may further comprise a lining carrier 24, visible in particular in [Fig. 2]. The lining carrier 24 may comprise a sheet metal, for example made of metallic material. The lining carrier 24 is connected, directly or indirectly, to the fixing face 22B of the lining 20.

[0089] The brake assembly 14 may also be provided with a shoe holder 28. The shoe holder 28 is connected to the lining holder 24. In particular, as visible in [Fig. 2], the shoe holder 28 may comprise a pin 30 shaped to pass through at least one orifice provided in the lining holder 24. Also, thanks to this pin 30, the plate 18 is secured to the shoe holder 28.

[0090] The brake assembly 14 is configured to move the shoe holder 28, and therefore the pad 18, substantially radially. During the braking phases of the vehicle, the brake assembly 14 is configured to move the pad 18 in a direction bringing it closer to the wheel 12 until the friction face 22A and the radially external surface 16 of the wheel 12 come into contact, as visible in [Fig. 3]. Once the braking phase is complete, the brake assembly 14 is configured to move the pad 18 in a direction moving it away from the wheel 12, so that the contact between the friction face 22A and the radially external surface 16 of the wheel 12 ceases. Indeed, outside of the braking phases, the pad 18 and the wheel 12 are at a distance from each other, as illustrated in [Fig. 1].

[0091] When the friction face 22A of the pad 18 and the radially external surface 16 of the wheel 12 come into contact during the braking phases, the wheel 12 is moving in rotation around the axis A. A friction force is thus produced between the friction face 22A and the radially external surface 16, which causes wear of both the lining 20 of the pad 18 and the radially external surface 16 of the wheel 12. Particles, generally polluting, are thus formed by the abrasion of the friction material of the lining 20 and the wheel 12. During this wear, the friction face 22A of the lining 20 takes on the shape of the radially external surface 16 of the wheel 12. The initial radius of curvature RI of the friction face 22A therefore changes progressively due to the wear of the lining 20.

[0092] In the following, when we speak of the “running-in phase”, we are referring to the time of the useful life of the pad 18 during which less than 90% of the friction face 22A is in contact with the wheel 12 during the braking phases of the vehicle.

[0093] As indicated previously, the lining 20 comprises at least one particle collection groove. Each collection groove is open at least partially on the friction face 22A, as will be detailed later. Each collection groove extends in depth between the friction face 22A and the fixing face 22B. Each of the collection grooves is preferably a blind groove at an end opposite its opening on the friction face 22A. Also, each collection groove is shaped to recover the polluting particles resulting from the wear of the lining 20 and the wheel 12, and thus prevent these particles from being released into the environment.

[0094] Several particular shapes that the at least one particle collection groove may have will now be described with reference to FIGS. 5A to 7. Of course, these shapes are not limiting.

[0095] In [Fig.5A], the lining 20 comprises a first main collection groove 30 and a second main collection groove 32.

[0096] The first main collection groove 30 is arranged near the front edge 22E. For example, the first main collection groove 30 is substantially parallel to the front edge 22E. The second main collection groove 32 is arranged near said rear edge 22F. For example, the second main collection groove 32 is substantially parallel to the rear edge 22F. As indicated previously, by “near the front / rear edge” is meant “at a distance from the front / rear edge less than or equal to 20% of the distance separating the front and rear edges, preferably less than or equal to 10% of the distance separating the front and rear edges”.

[0097] The presence of the main collection grooves 30, 32 near the front 22E and rear 22F edges makes it possible to guarantee the collection of polluting particles regardless of the direction of rotation of the wheel 12.

[0098] As can be seen from [Fig.5B], each main collection groove 30, 32 comprises a first portion 34 open on the friction face 22A and a second portion 36 covered by friction material of the friction face 22A. The second portion 36 of each groove 30, 32 is therefore immersed in the lining when the pad 18 is new or slightly worn. As will be explained in detail later, from a certain level of wear of the pad 18, the second part 36 of each groove 30, 32 emerges, that is to say, it also opens onto the friction face 22A.

[0099] In the non-limiting example of Figures 5A and 5B, the second portion 36 of each main collection groove 30, 32 is arranged under the chamfered edge 22C, without this being limiting. For example, alternatively, a portion of the second portion 36 could be immersed under the friction material of the friction face 22A, the remainder of the second portion 36 being immersed under the chamfered edge 22C.

[0100] The lining 20 of the plate 18 according to the example of [Fig.6] comprises the first and second main collection grooves 30, 32, as well as a secondary collection groove 38.

[0101] The secondary collection groove 38 is arranged between the first main collection groove 30 and the second main collection groove 32. According to a non-limiting example, the secondary collection groove 38 is located in a central position of the lining. As indicated previously, by “central position” is meant here a position located substantially at the same distance from the front edge 22E as from the rear edge 22F of the lining 20. Of course, the secondary collection groove 38 could be closer to one of the front edges 22E or rear edges 22F, than to the other of these edges 22E, 22F.

[0102] In [Fig.6], the secondary collection groove 38 extends substantially parallel to the main collection grooves 30, 32, without this being limiting. For example, the secondary collection groove could be substantially parallel to only one of the two grooves 30, 32, or extend in a direction not parallel to the main collection grooves 30, 32.

[0103] The secondary collection groove 38 may comprise a first portion open on the friction face 22A, similar to the first portion 34 of the main collection grooves 30, 32. The collection groove 38 may further comprise a second portion covered by friction material, similar to the second portion 36 of the main collection grooves 30, 32. The second portion of the secondary collection groove 38 may be disposed entirely under the chamfered edge 22C. Alternatively, a portion of the second portion of the secondary collection groove 38 may be submerged under the friction material of the friction face 22A, the remainder of the second portion of the secondary collection groove 38 being submerged under the chamfered edge 22C.As for the second part 36 of the main collecting grooves 30, 32, from a certain level of wear of the pad 18, the second part of the secondary collecting groove 38 emerges, that is to say, it also opens onto the friction face 22A. This will be explained in detail later.

[0104] In some cases, the secondary collection groove 38 is fully open on the friction face 22A even when the pad 18 is new. In such cases, advantageously the secondary collection groove 38 is shorter, for example it has no portion extending into the chamfered edge 22C.

[0105] It is noted that even if in this [Fig.6] a single secondary collection groove 38 is provided, the lining 20 could comprise a plurality of secondary collection grooves 38 as described above.

[0106] The presence of the main collection grooves 30, 32 and the secondary collection groove 38 has the advantage of ensuring that, whatever the radius of curvature of the friction face 22A of the pad, the support of the friction face 22A on the wheel 12 during the braking phases is made opposite one of the grooves 30, 32, 38. It is thus possible to collect in the grooves 30, 32, 38 a greater quantity of polluting particles emitted by the abrasion of the pad 18 and the wheel 12. In addition, as indicated previously, the presence of the main collection grooves 30, 32 near the front 22E and rear 22F edges makes it possible to guarantee the collection of the polluting particles whatever the direction of rotation of the wheel 12.

[0107] In some cases, the secondary collection groove 38 is fluidly connected to the first main collection groove 30 and to the second main collection groove 32. For this purpose, in the non-limiting example of [Fig. 7], a first transverse collection groove 40 and a second transverse collection groove 42 are provided in the lining 20.

[0108] The first transverse collection groove 40 fluidly connects the first main collection groove 30 and the secondary collection groove 38. In the non-limiting example of [Fig. 7], the first transverse collection groove 40 extends between one end of the first main collection groove 30 located opposite the axially external edge 22D of the lining 20, and one end of the secondary collection groove 38 located opposite the chamfered edge 22C. The first transverse collection groove 40 thus extends obliquely between the first main collection groove 30 and the secondary collection groove 38.

[0109] The second transverse collection groove 42 fluidly connects the second main collection groove 32 and the secondary collection groove 38. In the non-limiting example of [Fig. 7], the second transverse collection groove 42 extends between one end of the second main collection groove 32 located opposite the axially external edge 22D of the lining 20, and the end of the secondary collection groove 38 located opposite the chamfered edge 22C. The second transverse collection groove 42 thus extends obliquely between the second main collection groove 32 and the secondary collection groove 38.

[0110] The first transverse collection groove 40 and the second collection groove transverse 42 are advantageously open on the friction face 22A. In the non-limiting example of [Fig.7], the first and second transverse collection grooves 40, 42 are open over their entire extension on the friction face 22A. It is however possible to provide submerged parts on each of the first and second transverse collection grooves 40, 42.

[0111] Thanks to the presence of the transverse collection grooves 40, 42, the entire length of the lining 20 between the main collection grooves 30, 32 is crossed by at least one particle collection groove. This increases the surface area of ​​the lining occupied by the collection grooves, which makes it possible to increase the quantity of polluting particles collected in the grooves and therefore, which are not released into the environment.

[0112] The fact that the first and second transverse collecting grooves 40, 42 extend at an angle is also advantageous. In particular, as indicated previously, during the braking phases, the radially external surface 16 of the wheel 12 wears concomitantly with the wear of the lining 20. The portion of the radially external surface 16 of the wheel 12 which is at each instant of the braking phase directly opposite one of the collecting grooves is not worn at this instant. Indeed, each collecting groove forms a recess in the friction face 22A. Each collecting groove therefore prevents there from being friction forces between the friction face 22A and the radially external surface 16 of the wheel 12.If the transverse collecting grooves 40, 42 connected the main collecting grooves 30, 32 and the secondary collecting groove 38 in a direction tangential to the portion of the radially external surface 16 which is in contact with the lining 20 during the braking phases, an annular portion of the radially external surface 16 of the wheel 12 would never be in contact with the friction material of the friction face 22A. Ultimately, the radially external surface 16 of the wheel 12 would have an excess thickness on this annular portion relative to the rest of the radially external surface 16 of the wheel 12. Such an excess thickness can damage the rail on which the wheel 12 moves, and / or cause the vehicle to derail.In the present case, thanks to the transverse collection grooves 40, 42 at an angle, it is guaranteed that the contact time between any portion of the radially external surface 16 of the wheel 12 is negligible compared to the time that such a portion is in contact with the friction material of the lining 20. The wheel 12 is thus worn in a homogeneous manner, which avoids the appearance of excess thicknesses on its radially external surface 16.

[0113] In order to suck up the polluting particles collected in each groove 30, 32, 38, 40, 42, the plate 18 further comprises at least one suction hole, not visible in the figures. This suction hole is in particular arranged in the lining 20 of the plate 18 so as to fluidly connect one of the collection grooves 30, 32, 38, 40, 42 to the external environment.

[0114] According to one example, an individual suction hole may be provided for each of the main collection grooves 30, 32 and for the secondary collection groove 38. This configuration is notably implemented when the main 30, 32 and secondary 38 collection grooves are not fluidically connected to each other, as is the case in the exemplary embodiments of FIGS. 5A and 6. Advantageously, but without this being limiting, the individual suction hole is arranged at one end of the respective collection groove 30, 32, 38, which makes it possible to concentrate the suction of the particles at this end.

[0115] According to another example, the plate 18 comprises a single suction hole opening onto one of the main collection grooves 30, 32 or the secondary collection groove 38. This configuration is notably implemented when the main collection grooves 30, 32 and the secondary collection groove 38 are fluidically connected to each other, as in the example of [Fig. 7]. Advantageously, but without this being limiting, the suction hole is arranged at one end of one of the main collection grooves 30, 32 or secondary 38. The suction of the particles is thus concentrated at this end. According to one example, the suction hole opens onto one end of the secondary collection groove 38 which is opposite the axially external edge 22D of the lining 20.

[0116] Each suction hole is intended to be connected to a vacuum source (not shown). The vacuum source is for example a particle vacuum cleaner. Communication means 44, visible in [Fig.l], can connect the vacuum source to the corresponding suction hole. The particles collected in the collection grooves 30, 32, 38, 40, 42 can thus be sucked up. The communication means 44 comprise for example a flexible pneumatic hose.

[0117] As visible in Figures 5A, 6 and 7, the lining 20 may further comprise at least one orifice 46 which passes through the chamfered edge 22C. In particular, each orifice 46 passes through the chamfered edge 22C and opens onto one of the main collection grooves 30, 32 or the secondary collection groove 38. An air flow can thus enter the grooves 30, 32, 38 through the orifice 46. By the action of the vacuum source, this flow then circulates in the collection grooves until it reaches the suction hole and the pipe 44, which allows the evacuation of the particles collected in the collection grooves of the lining 20. Thanks to each orifice 46, the particle suction performance is independent of the level of wear of the lining 20.

[0118] As indicated previously, the friction face 22A is substantially curved. However, the radius of curvature RI of the friction face 22A when the pad 18 is new is generally different from the radius of curvature R2 of the portion of the radially external surface 16 on which the friction face 22A bears when braking phases, whether the wheel is new or worn. The surface area of ​​the friction face 22A which comes into contact with the wheel 12 during the braking phases increases as the lining is worn, which causes, as indicated above, the friction face 22A to gradually take on the shape of the wheel.

[0119] Figures 8 to 11 schematically show the contact surface of the friction face 22A of the pad 18 on the wheel 12 during braking phases for four different levels of wear of the friction face 22A as a function of: - the type of grooves arranged in the lining 20; and - whether the wheel 12 is new or worn.

[0120] As indicated previously, we assume here that the radius of curvature RI of the friction face 22A is greater than the radius of curvature R2 of the portion of the wheel 12 on which the pad 18 comes to bear during the braking phases. Also, as long as the friction face 22A has not taken on the shape of this portion of the wheel 12, the friction face 22A presses its central part on the wheel, its ends remaining free.

[0121] Each of these figures comprises a table including five X rows and three Y columns. The table of each [Fig.8] to 11 therefore comprises fifteen XY boxes.

[0122] Each line X corresponds to a type of plate 18 studied according to the type of grooves arranged in the lining 20. The column Y=A represents the type of plate 18 studied. Also, as visible in boxes IA to 5A: - the line X=1 corresponds to the prior art pads which comprise two grooves at the ends which extend over almost the entire width of the pad 18 and which are completely open on the friction face from the start of the useful life of the pad 18; - line X=2 corresponds to the prior art pads which include two grooves at shorter ends than in the example of line 1 and which are completely open on the friction face from the start of the useful life of the pad 18; - the line X=3 corresponds to the plates as described above with reference to figures 5A and 5B (that is to say, the plates comprising the two main collection grooves 30, 32); - the line X=4 corresponds to the plates as described above with reference to [Fig.6] (i.e., the plates comprising the two main collection grooves 30, 32 and the secondary collection groove 38); and - the line X=5 corresponds to the plates as described above with reference to [Fig.7] (i.e., the plates comprising the two main collection grooves 30, 32 and the secondary collection groove 38 connected to each other by the transverse collection grooves 40, 42).

[0123] Column Y=N shows for each of these types of platelets 18 what is the contact surface of the friction face 22A with the wheel 12 during the braking phases of the vehicle when the wheel 12 is new. Column Y=U shows for each of these types of pads 18 what is the contact surface of the friction face 22A with the wheel 12 during the braking phases of the vehicle when the wheel 12 is worn.

[0124] The differences between figures 8, 9, 10 and 11 are due to the fact that in each of these figures, the level of wear of the friction face 22A is different, this level of wear increasing from [Fig.8] to [Fig. 11].

[0125] The columns Y=N and Y=U of [Fig.8] represent the contact surface of the friction face 22A which comes to bear on the radially external surface 16 of the new (Y=N) or worn (Y=U) wheel when the pad 18 first presses on the wheel 12. In other words, in [Fig.8] the friction face 22A is not worn before the contact between the friction face 22A and the wheel 12.

[0126] Figures 9, 10 and 11 show the contact surface of the friction face 22A on the radially external surface 16 of the new (Y=N) or worn (Y=U) wheel at different wear levels of the friction face 22A. The wear level of the friction face 22A increases between [Fig.9] and [Fig.11], [Fig.10] corresponding to the friction face 22A having an intermediate wear level between that of [Fig.9] and that of [Fig.11],

[0127] In these figures 8 to 11, the areas shown in hatching correspond to the areas of the friction face 22 for which the polluting particles generated during the braking phases can be collected in the collection grooves for their suction when the wheel 12 rotates in a first direction. The unhatched areas correspond to the areas of the friction face 22 for which the polluting particles generated during the braking phases are mainly released into the environment and therefore not sucked in, when the wheel 12 rotates in this first direction. It is noted that if the wheel 12 rotated in a second direction opposite to the first direction, the hatched and unhatched areas would be reversed compared to those of figures 8 to 11.

[0128] Reference is now made to [Fig.8], which corresponds as indicated previously to the first pressing of the new pad on the wheel 12.

[0129] As visible in boxes IN, 2N, 1U and 2U, during this first pressing, the pads having grooves according to the prior art have a contact surface of the friction face 22A with the new wheel 12 (boxes IN and 2N) or worn wheel (boxes 1U and 2U) which does not include any portion of the collection grooves. Also, the polluting particles generated during this first pressing are very largely, or even entirely, released into the environment.

[0130] In the case of the pad 18 according to figures 5A and 5B, the contact surface of the friction face 22A with the new wheel 12 (case 3N) or worn wheel (case 3U) is similar to that of the pads of the prior art. Indeed, the contact surface of the friction face 22A with the wheel 12 does not include any portion of the main collection grooves 30, 32. Also, the polluting particles generated during this first support are very largely, or even entirely, released into the environment.

[0131] The situation is different for the pads 18 having collection grooves arranged according to the examples of FIGS. 6 and 7 described above. In these examples, secondary collection grooves 38 are provided. As indicated previously, such secondary collection grooves 38 are arranged on a central portion of the friction face 22A. Also, during the first pressing of the friction face on the wheel 12, a portion of the secondary collection groove 38 is included in the contact surface of the friction face 22A on the new wheel 12 (cases 4N and 5N) or worn wheel (cases 4U and 5U). This portion of the collection groove 38 is therefore closed by the radially external surface 16 of the wheel 12.This makes it possible to collect in the secondary collection groove 38 the polluting particles generated by the part of the contact surface of the friction face 22A which is located in front of the portion of the secondary collection groove 38 closed according to the directions of rotation R of the wheel. This part of the contact surface for which the particles generated can be collected in the secondary collection groove 38 is shown in hatching on the boxes 4N, 5N, 4U and 5U.

[0132] It should be noted, however, that the entire secondary collection groove 38 is not in the contact surface of the friction face 22A with the wheel 12 because of the frustoconical shape of the radially external surface of the wheel 12. Also, the secondary collection groove 38 is not, during this first pressure, put under vacuum in a homogeneous manner, since the ambient air can access it through the portion of the groove 38 that is not blocked. In the case of the example in [Fig. 7], the ambient air can also access the blocked portion of the groove 38 through the main collection grooves 30, 32 and transverse collection grooves 40, 42, with which the secondary collection groove 38 is fluidically connected. Also, a portion of the polluting particles collected in the secondary collection groove 38 is finally released into the environment before suction.For example, when a portion of the closed groove, in this case the secondary collection groove 38, is not closed, the rate of particles collected in this groove which is finally sucked up can be between 30% and 60%, or between 35% and 50%. For example, this rate can be substantially equal to 40%.

[0133] Reference is now made to [Fig.9], in which the wear level of the friction face 22A is greater than that of [Fig.8].

[0134] In the case of pads having grooves according to the prior art, the contact surface of the friction face 22A with the new wheel 12 (boxes IN and 2N) this time comprises a portion of the collection grooves arranged at the ends of these pads according to the prior art. This portion of the collection grooves is therefore closed by the radially external surface 16 of the wheel 12. This makes it possible to collect in the collection grooves at the ends of the pad the polluting particles generated by the part of the contact surface of the friction face 22A which is located in front of the portion of the collection grooves closed in the directions of rotation R of the wheel. This part of the contact surface corresponds to the hatched part on boxes IN and 2N. However, as explained previously for the cases of boxes 4N, 5N, 4U and 5U of [Fig.8], given that the collection grooves at the ends of these pads according to the prior art are not completely closed, these grooves are not put under vacuum in a homogeneous manner and part of the collected particles are finally released into the environment through the unclosed portion of the grooves.The rate of collected particles that is finally sucked up can therefore be between 30% and 60%, or between 35% and 50%. For example, this rate can be approximately equal to 40%.

[0135] It is noted that with the level of wear of [Fig.9], when the pads according to the prior art come to bear against a worn wheel, the collection grooves provided are not included in the contact surface of the friction face 22A with the wheel 12 (see boxes 1U and 2U). Also, at this level of wear of the friction face 22A and when the wheel is worn, the polluting particles generated by the abrasion of the friction face 22A and the wheel are very largely, or even entirely, released into the environment.

[0136] In the case of the pad 18 according to FIGS. 5A and 5B, the contact surface of the friction face 22A with the new (case 3N) or worn (case 3U) wheel 12 is similar to that of the pads of the prior art. Also, in the case of the new wheel, a part of the contact surface of the friction face 22A comprises a portion of the main collection grooves 30, 32, which makes it possible to collect the particles from the hatched area of ​​case 3N. However, the entire main collection groove 30, 32 is not blocked by the wheel 12. These grooves 30, 32 are therefore not placed under vacuum uniformly and consequently a portion of the collected particles are ultimately released into the environment through the unblocked portion of the grooves 30, 32. The rate of collected particles that is ultimately sucked up may therefore be between 30% and 60%, or between 35% and 50%. For example, this rate may be substantially equal to 40%.In the case of the worn wheel, the contact surface of the friction face 22A does not include any portion of the main collection grooves 30, 32. Consequently, the polluting particles generated by the abrasion of the friction face 22A and the worn wheel are largely, or even entirely, released into the environment.

[0137] For the example in [Fig.6], the situation is the same as for the wear level of [Fig.8], but since the contact surface of the friction face 22A with the wheel 12, new or worn, is larger, the portion of the secondary collection groove 38 which is closed by the radially external surface 16 of the wheel 12 is also larger. This makes it possible to collect more polluting particles in the secondary collection groove 38. As in the previous cases, the collected polluting particles come from the part of the contact surface of the friction face 22A which is located in front of the portion of the secondary collection groove 38 closed in the direction of rotation R of the wheel (hatched part in FIGS. 4N and 4U).However, the secondary collection groove 38 is not completely closed, so that the depression inside it is not homogeneous, which causes the rate of collected particles which is actually sucked in to be within the ranges indicated previously (30% to 60%, or 35% to 50%, for example 40%).

[0138] For the example of [Fig.7], when the friction face 22A comes into contact with the worn wheel 12, the situation at the wear level of the friction face 22A of [Fig.9] is similar to that of the wear level of [Fig.8], but with a larger contact surface (see box 5U). This closes a larger portion of the secondary collection groove 38. The part of the contact surface of the friction face 22A for which the generated particles can be collected in the groove 38 is therefore larger (see hatched part of box 5U). The total quantity of particles collected in the secondary collection groove 38 is therefore greater than that of [Fig.8]. However, since the secondary collection groove 38 is still not completely blocked, the rate of particles collected in the groove 38 which is actually sucked is within the ranges indicated previously (30% to 60%, or 35% to 50%, for example 40%).

[0139] In the case of contact between the pad of [Fig.7] and the new wheel, the contact surface is also larger at the wear level of [Fig.9] than at that of [Fig.8]. As visible in box 5N, the contact surface now comprises not only a portion of the secondary collection groove 38, but also a portion of the main collection grooves 30, 32, and a portion of the transverse collection grooves 40, 42. The portion of the contact surface of the friction face 22A for which the generated particles can be collected in the grooves 30, 32, 38, 40, 42 is therefore larger and corresponds to the hatched portion in box 5N. However, since none of the grooves 30, 32, 38, 40, 42 is still completely blocked, the rate of particles collected in the groove 38 which is actually sucked is within the ranges indicated previously (30% to 60%, or 35% to 50%, for example 40%).

[0140] Reference is now made to [Fig. 10], in which the wear level of the friction face 22A is greater than that of [Fig.9].

[0141] In the case of the prior art plates of line X=1 of the table (corresponding to those which include two grooves at the ends which extend over almost the entire width of the pad), the contact surface of the friction face 22A on the new wheel 12 is such that the grooves at the ends are completely blocked except at their end located on the chamfered edge of the pad. The particles from the entire hatched area in box IN can therefore be collected in the grooves at the ends, but a portion is released into the environment through the unblocked end before being sucked in. The rate of particles collected in the grooves at the ends of the pad which is actually sucked in is therefore within the ranges indicated previously (30% to 60%, or 35% to 50%, for example 40%).

[0142] When the wheel is worn, the contact surface of the pads of the prior art of the line X=1 still does not include the collection grooves of the ends of the pad (box 1U). Also, at this level of wear of the friction face 22A and when the wheel is worn, the polluting particles generated by the abrasion of the friction face 22A and the wheel are very largely, or even entirely, released into the environment.

[0143] In the case of the prior art pads of line X=2 of the table (corresponding to those which comprise two grooves shorter than those of line X=1), the contact surface of the friction face 22A on the wheel comprises all of the grooves of the ends (box 2N). The grooves are therefore placed under vacuum in a homogeneous manner, and the risk of leakage of the particles collected in the grooves is very reduced. When the collection grooves are completely blocked, the percentage of the particles collected in the grooves which is actually sucked up is between 80% and 100%. For example, the percentage of particles collected in the grooves which is actually sucked up is equal to 90%.

[0144] When the wheel is worn, the contact surface of the pads of the prior art of the line X=2 still does not include the collection grooves of the ends of the pad (box 2U). Also, at this level of wear of the friction face 22A and when the wheel is worn, the polluting particles generated by the abrasion of the friction face 22A and the wheel are very largely, or even entirely, released into the environment.

[0145] In the examples of Figures 5A to 7, when the contact of the friction face 22A is made with the new wheel, the entire first part 34 of the main collection grooves 30, 32, and possibly secondary 38, as well as all of the transverse collection grooves 40, 42 are closed by the wheel (boxes 3N, 4N and 5N). It is noted that at the wear level of [Fig. 10], the second part 36 of the grooves comprising an immersed part has not yet emerged. Also, all the grooves 30, 32, 38, 40, 42 are placed under vacuum in a homogeneous manner, and the risk of leakage of the particles collected in the grooves 30, 32, 38, 40, 42 is very small. As previously indicated, when the grooves are completely closed, the percentage of particles collected in the grooves that is actually sucked up is between 80% and 100%. For example, the percentage of particles collected in the grooves that is actually sucked up is 90%.

[0146] For the example of [Fig.5A], when the contact of the friction face 22A is made with the worn wheel, the contact surface of the friction face 22A still does not include the collection grooves 30, 32 (case 3U). Also, at this level of wear of the friction face 22A and when the wheel is worn, the polluting particles generated by the abrasion of the friction face 22A and the wheel 12 are very largely, or even entirely, released into the environment.

[0147] For the example of [Fig.6], when the contact of the friction face 22A is made with the worn wheel, the contact surface of the friction face 22A is similar to that of the wear level of [Fig.9], but with a larger contact surface (see box 4U). This closes a larger portion of the secondary collection groove 38. The part of the contact surface of the friction face 22A for which the generated particles can be collected in the groove 38 is therefore larger (see hatched part of box 4U). The total quantity of particles collected in the secondary collection groove 38 is therefore greater than that of [Fig.9]. However, since the secondary collection groove 38 is still not completely blocked, the rate of particles collected in the groove 38 which is actually sucked is within the ranges indicated previously (30% to 60%, or 35% to 50%, for example 40%).

[0148] For the example of [Fig.7], when the contact of the friction face is made with the worn wheel, the contact surface of the friction face 22A includes not only the secondary collection groove 38, but also the transverse collection surfaces 40, 42 (case 5U). However, the main collection grooves 30, 32, which are fluidically connected to the transverse collection grooves 40, 42 and secondary 38, are not included in this contact surface. Also, although the main collection groove 38 and the transverse collection grooves 40, 42 are completely blocked, ambient air can enter these grooves via the main collection grooves 30, 32, which are not blocked. The grooves 38, 40, 42 are therefore not placed under uniform depression and some of the collected particles can therefore escape through the main collection grooves 30, 32.Therefore, and the rate of particles collected in the groove 38 which is actually sucked is within the ranges indicated previously (30% to 60%, or 35% to 50%, for example 40%).

[0149] Reference is now made to [Fig. 11], in which the wear level of the friction face 22A is greater than that of [Fig. 10]. At this wear level, whether the wheel is new or worn, and for all types of pads shown on the lines X=1 to X=5, the collection grooves provided in the lining are completely blocked by the wheel 12 during braking phases. Indeed, at this level of wear, the friction face 22A has already perfectly matched the shape of the wheel 12. The particles from the entire friction surface 22A can therefore be collected in the collection grooves. Since the grooves are completely blocked, the percentage of collected particles actually sucked up is between 80% and 100%. For example, the percentage of particles collected in the grooves that is actually sucked up is equal to 90%.

[0150] The graph in [Fig. 12] represents, for the case where the wheel 12 is new, the evolution of the cumulative efficiency of the particle suction (y-axis) as a function of the service life rate of the pad 18, in particular of its lining 20 (x-axis). The graph in [Fig. 13] represents this same evolution but for the case where the wheel 12 is worn.

[0151] In these two graphs, curve 50 represents this evolution for the prior art wafers of line X=1 of the tables in Figures 8 to 11. Curve 52 represents this evolution for the prior art wafers of line X=2 of the tables in Figures 8 to 11. Curve 54 represents this evolution for the wafers according to the example in [Fig.5A]. Curve 56 represents this evolution for the wafers according to the example in [Fig.6]. Curve 58 represents this evolution for the wafers according to the example in [Fig.7].

[0152] From the graph of [Fig. 12], it can be deduced that the linings 20 with immersed grooves like those of the examples of FIGS. 5A to 7 are very efficient at the beginning of the life of the lining 20 when the wheel 12 is new. Indeed, up to 10% of the life of the lining 20, the suction efficiency increases very quickly, until reaching 70% suction efficiency. Then, between 10% and 30% of the life of the lining 20, the suction efficiency continues to increase but more slowly, to reach 75% efficiency. From 30% of the life of the lining, the suction efficiency is maintained at around 75%. In the graph of [Fig.12], curves 54, 56, 58 are coincident, which shows that all examples in Figures 5A to 7 have similar efficiencies.

[0153] From the graph of [Fig. 12] it is also deduced that the use of short grooves like those of the prior art of the line X=2 of figures 8 to 11 has, at the beginning of the life of the lining and when the wheel is new, a particle suction efficiency similar to that of the linings 20 with immersed grooves of figures 5A to 8. Indeed, up to 10% of the life of the lining, the curve 52 follows the trend of the curves 54, 56 and 58, and it reaches 70% efficiency. However, from 10% of the life of the lining, the suction efficiency decreases compared to the linings 20 with immersed grooves. This is due to the fact that the short grooves of the prior art inserts have a constant size throughout their life. These short grooves may be similar in size to the first portion 34 of the grooves with submerged portions of Figures 5A to 7. Also, as long as the insert with short grooves according to the prior art is not worn on the portion of the insert that does not include grooves, the suction efficiency is the same as in the inserts 20 with submerged grooves. However, once the wear of these portions without grooves begins, in the case of the insert with short grooves according to the prior art the particles generated by the wear of this portion are neither collected nor sucked (since, as indicated, in this case of the prior art the wear of the insert does not change the size of the collection grooves).In contrast, in the case of the linings 20 with submerged grooves, wear of the pad 18 causes the second portions 36 of the grooves with submerged portions to emerge. Thus, in the linings 20 according to FIGS. 5A to 7, the size of the collection grooves increases during wear of the pad 18, which makes it possible to collect more particles as the lining is worn. These reasons explain why the suction efficiency decreases from 10% of service life for the pads with short grooves according to the prior art, while it continues to increase for the linings 20 with submerged grooves of FIGS. 5A to 7.

[0154] Finally, the graph in [Fig. 12] shows that when the wheel is new, the use of a pad with long grooves of the prior art, such as those of line X=1 in Figures 8 to 11, is more effective than the use of short grooves such as those of line X=2 in Figures 8 to 11 from 70% of the lining life. Indeed, before 70% of the lining life, the end of the long grooves of the prior art is not blocked during braking phases, which allows the escape of particles collected in the grooves. On the contrary, in the short grooves of the prior art, the sealing of the grooves occurs more quickly.However, as explained above, from 10% of the lining life, the worn surface of the lining increases, but the short grooves of the prior art do not increase their size, which causes a significant release of particles into the environment. In the case of the long grooves of the prior art, before 70% of the lining life, these grooves are not sealed. However, from 70% of the lining life, the ends of these long grooves begin to be blocked by the wheel during braking phases, so that the suction efficiency increases.

[0155] From the graph of [Fig. 13] it can be deduced that, when the wheel is worn, the linings comprising at least the main collection grooves 30, 32 and the secondary collection groove 38, like the examples of figures 6 and 7, have a suction efficiency superior compared to the linings without secondary collection groove 38. Furthermore, for the initial 30% of the lining life, the lining 20 comprising the transverse collection grooves 40, 42 which connect the main collection grooves 30, 32 to the secondary collection groove 38 have the best efficiency among the different types of lining analyzed. From 30% of the lining life, the suction efficiency is similar for the lining according to the example of [Fig.6] and for the lining 20 according to the example of [Fig.7].

[0156] The present disclosure is not limited to the examples of brake pads described above, only by way of example, but it encompasses all the variants that may be envisaged by those skilled in the art in the context of the desired protection. For example, according to a variant not illustrated, the friction face of the lining of the pad could have two different radii of curvature. For example, the friction face could have a first smaller radius of curvature in the center and a second wider radius of curvature at the ends. This makes it possible to reduce the duration of the running-in phase.

Claims

Demands

1. Brake pad (18), the pad (18) comprising a friction material lining (20) having a friction face (22A) intended to come into contact with a rotating element (12), a front edge (22E) and a rear edge (22F), the lining being provided with at least one main collection groove (30, 32), the pad (18) further comprising at least one suction hole intended to be in fluidic communication with said at least one main collection groove (30, 32), said at least one suction hole also being intended to be connected to a vacuum source, in which said at least one main collection groove (30, 32) comprises a first open portion (34) on the friction face and a second portion (36) covered by friction material of the friction face (22A).

2. Plate (18) according to claim 1, wherein said friction face (22A) comprises a chamfered edge (22C) extending between said front edge (22E) and said rear edge (22F), the second part (36) of at least one main collection groove (30, 32) being disposed at least in part under said chamfered edge (22C).

3. Plate (18) according to claim 1 or 2, wherein the trim (20) comprises a first main collection groove (30) disposed near said front edge (22E) and a second main collection groove (32) disposed near said rear edge (22F).

4. Plate (18) according to claim 3, wherein the first main collection groove (30) extends lengthwise substantially parallel to said front edge (22E) and the second main collection groove (32) extends lengthwise substantially parallel to said rear edge (22F).

5. Plate (18) according to any one of claims 3 or 4, further comprising a secondary collection groove (38) disposed between the first main collection groove (30) and the second main collection groove (32), said at least one secondary collection groove (38) being at least partially open on said friction face (22A).

6. Plate (18) according to claim 5, wherein said secondary collection groove (38) comprises a first part open on said friction face (22A) and a second part covered by friction material of the friction face (22A).

7. Plate (18) according to any one of claims 5 to 7, wherein said secondary collection groove (38) is fluidly connected to said first main collection groove (30) and to said second main collection groove (32).

8. Plate (18) according to any one of claims 5 to 8, further comprising a first transverse collection groove (40) fluidly connecting the first main collection groove (30) to the secondary collection groove (38), and a second transverse collection groove (42) fluidly connecting the second main collection groove (32) to the secondary collection groove (38).

9. Plate (18) according to claim 8, wherein the first transverse collection groove (40) is at least partially open on the friction face (22A) and extends obliquely between the first main collection groove (30) and the secondary collection groove (38), and the second transverse collection groove (42) is at least partially open on the friction face (22A) and extends obliquely between the second main collection groove (32) and the secondary collection groove (38).

10. Plate (18) according to any one of claims 7 to 9, comprising a single suction hole opening onto one of said secondary collection groove, said first main collection groove and said second main collection groove.

11. Plate (18) according to any one of claims 3 to 10, wherein the first main collection groove (30) extends in depth not parallel to said front edge (22E) and the second main collection groove (32) extends in depth not parallel to said rear edge (22F).

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